Research On The Control Strategy Of Multi-phase Induction Machine Under Open Phases Operation

Compared with three-phase induction machine, the multi-phase induction machine have many advantages such as high reliability and reducing the amplitude of torque pulsation. The multi-phase induction machine is still running when one phase or multi-phases are fault, which is the most significant merit of it and arose more and more attentions. In the paper, the mathematical models, the performances and the control strategy are analyzed and simulated when multi-phase motor operated in open phases condition.According to the principle of electromechanical energy conversion, the mathematical models of multi-phase induction machine under normal condition are built by using the space vector decoupling. A six-phase machine was studied. The mathematical models which are in open phases condition are built. Then the mathematical models which are suitable for multi-phase induction machine fault condition are deduced.According to the mathematic models of multi-phase induction machine, the performance parameters are compared by using symmetrical component method when the six-phase induction machine operate in normal and fault condition. Some conclusions are obtained: The remaining phase currents will be increased. The steady-state average torque is dropped and the torque pulsation are caused. The simulation models under normal and open phases operations in Matlab are built. The simulation results verified the performance parameters alternation.The flux oriented control scheme under normal operation is not suitable for the fault condition. In the paper, a vector control strategy which can be used in open phase conditions was presented. By using carrier wave PWM based on effective time method and vetor control scheme based on rotor field orientation, the simulation models of six-phase induction machine under fault condition in Matlab are built. The simulation results verified the theoretical analyse and the control strategies.At last, the Direct Torque Control (DTC) strategy is researched when six-phase induction machine work in fault condition. According to the defacts of conventional DTC, a new DTC is represented. The switch list is not needed and carrier wave SVPWM method is used in DTC. Then the simulation models are built in Matlab and verified the proposed scheme.